The cloud chamber bowls themselves are sections of 12-gallon Pyrex carboys, suspended from a redwood frame on ropes. These difficult-to-find and impossible-to-tune glass gongs are played very carefully by a percussionist who risks the anguish of splintered disaster. The original bowls were found at the Radiation Laboratory of the University of California, Berkeley, and had been used as cloud-chambers to trace the paths of sub-atomic particles.